PARTS AND FUNCTIONS. 59 



CHAPTER VII. 



OF THE MECHANICAL AND IMMECHANICAL 

 PARTS AND FUNCTIONS OF ANIMALS AND 

 VEGETABLES. 



It i? not that every part of an animal or vegetable has 

 not proceeded from a contriving mind ; or that every part is 

 not constructed with a view to its proper end and purpose, 

 according to the laws belonging to, and governing the sub- 

 stance or the action made use of in that part ; or that each 

 part is not so constructed as to effectuate its purpose while 

 it operates according to these laws ; but it is because thfese 

 laws themselves are not in all cases equally understood, or, 

 what amounts to nearly the same thing, are not equally ex- 

 emplified in more simple processes and more simple n^a- 

 chines, that we lay down the distinction here proposed, be- 

 tween the mechanical and imniechanical parts of animals. 



For instance, the principle of muscular motion, namely, 

 upon what cause the swelling of the belly of the muscle, 

 and consequent contraction of its tendons, either by an act 

 of the will, or by involuntary irritation, depends, is wholly 

 unknown to us. The substance employed, whether it be 

 fluid, gaseous, elastic, electrical, or none of these, or nothing 

 resembling these, is also unknown to us : of course, the laws 

 belonging to that substance, and which regulate its action, 

 are unknown to us. We see nothing similar to this contrac- 

 tion in any machine which we can make, or any process 

 which we can execute. So far, it is confessed, we are in 

 ignorance, but no farther. This power and principle, from 

 whatever cause it proceeds, being assumed, the collocation 

 of the fibres to receive the principle, the disposition of the 

 muscles for the use and application of the power, is mechan- 

 ical, and is as intelhgible as the adjustment of the wires 

 and strings by which a puppet is moved. "VYc see, there- 

 fore, as far as respects the subject before us, Avhat is not me 



